Message-Id: <5.1.1.5.2.20031120121714.01739268@popserve.lerc.nasa.gov>
Date: Thu, 20 Nov 2003 12:26:47 -0500
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: Joseph M Berki <Joseph.M.Berki@grc.nasa.gov>
Subject: Re: [FlyRotary] Re: radiator size
In-Reply-To: <list-2753036@logan.com>
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Ed,
         No it is not a rotary it is a soob.  My point was that if we 
optimize the inlet we can get the radiator to the correct size.  Thank you 
for providing the btu numbers that i will start to determine rad size with. 
Charlie has a soob in a Vari EZ direct drive and his power level is 
probably quite low.  He is currently working on a Cozy with a 13b and we 
are trying to determine the rad size and cooling layout. My project is 
similar to his so we are sharing ideas.

Joe


>Joe, I have no problem believing that Charlie has adequate cooling at
>cruise.  With a 5 g/h fuel burn (if using a rotary) Charlie  would be only
>producing approx 55 HP.  That would mean he would need to get rid of approx
>1700 btu/min by radiator and approx 850 btu/min by oil cooler.  Even using
>only one core as radiator, at that power level, he could get adequate
>cooling at airspeeds as low as 100 MPH.  I suspect that at take off he is of
>course producing more power and waste heat.   At 200MPH at those fuel burn
>rates and only one core, he would still have over 150% total reserve cooling
>capacity.
>
>Smaller power levels = smaller cooling needs.  So it all depends on your
>power levels and airspeeds (or more correctly mass airflow rate through your
>radiators).
>
>I think you really have to look at the btu of waste heat you need to get rid
>of which is directly dependent on the power being produced and then at the
>airspeed available for mass air flow through your radiators.  Then you have
>to decide which part of the operational regime you want to design your
>cooling system for.  To miminize cooling drag, you might start looking at
>the requirements for your cruise regime - particuarly since you will spend
>98% of your operating time there.   On the other hand, if you are building a
>bush plane that you expect to spend a lot of time at low airspeeds and high
>power settings climbing in and out of mountainous terrain then you might
>want to lean the design point more toward that operating regime (high power
>low airspeed).  I think that these type considerations form a reasonable
>starting point.
>
>  Clearly if you don't do the radiator sizing correctly - then NACA ducts
>with vortex generators or mustange like scoops or any other arrangement is
>not going to make up for inaqduately sized radiators.
>
>My 0.02 worth.
>Ed
>Ed Anderson
>RV-6A N494BW Rotary Powered
>Matthews, NC
>eanderson@carolina.rr.com
>
>
>
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